Dear Mark: Nuts

AcornsDear Mark,

Can you give me more explanation about nuts and seeds? I eat a ton of them and am always confused about which ones are actually nuts and which are seeds and which are legumes. Does it make any difference if you eat them whole, roasted, raw or as nut butter?

Thanks to reader Charlotte for these questions in response to last week’s “Get Primal” post. The classification question does get tricky.

Cashew Fruit

Nuts themselves are actually a kind of fruit, specifically “dried fruit.” But not everything we consider nuts are really nuts. Some are actually seeds, often within fruits or even legumes. A hazelnut is, indeed, a nut. An acorn is also a variety of “true” nut, as are pecans, walnuts and chestnuts. But an almond, for example, is a seed inside a fleshy fruit’s (a.k.a. drupe’s) pit. A pistachio is a seed within a fleshy fruit. Pine nuts are seeds. Cashews are seeds. Peanuts are the seeds of a legume. Technically speaking, all nuts are fruits, and a “true” nut is indehiscent (they don’t – by themselves – open to spread seeds), hard-shelled and generally one-seeded.

But let’s look at all this from a practical perspective: what’s good to eat? “Nuts” in the broad culinary classification contain protein. Big plus. They tend to be high in certain B-vitamins, vitamin E, and many minerals. Another plus. Low carb. Yet another plus. But not all “nuts” are created equal. Some, like peanuts, have high levels of omega-6. As we’ve said a lot lately, we moderns seem to get way more than enough of omega-6 in our diets. Walnuts, for example, offer a nice dose of omega-3. Almonds are a great source of phytochemicals, contain calcium, and are even lower in carbs than most.


And then there’s the issue of aflatoxins, dangerous metabolites produced by certain mold varieties. Aflatoxins are common in what we usually refer to as “tree” and “ground” nuts, including almonds, walnuts and pecans as well as peanuts and cashews. The toxin has been shown to have carcinogenic, mutagenic and immunosuppressive properties. While certain farming practices can reduce the problem, the aflatoxin related molds are considered at least somewhat inevitable. Peanuts are often said to have the highest concentration of aflatoxins, and they are among the most heavily (pesticide) sprayed food grown.

Nut Butter

In terms of roasted versus raw, I’d recommend raw to avoid the oxidation that happens during heating. However, there are increasing challenges to the sale of truly raw (untreated) nuts. The Cornucopia Institute offers a great deal of information on the recent raw almond controversy, but all California grown almonds now have either chemical or high heat treatments. The change came after raw almonds were believed to be connected with two salmonella cases, although farming practices vary considerably and may have contributed to the problem. Regarding nut butter versus nuts themselves, it’s your choice. However, be sure to select nut butter (I recommend almond butter) without added ingredients, especially added sugars. And, again, I’d favor raw and organic over conventional and roasted.

Thanks for the questions, everyone!

steffenz, Marcio Cabral de Moura, sproutgrrl Flickr Photos (CC)

Further Reading:

Dear Mark: Beans/Legumes

Smart Fuel: Walnut Oil

Modern Forager: Ten Staples of a Well-Stocked Kitchen

Subscribe to Mark’s Daily Apple feeds

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About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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42 thoughts on “Dear Mark: Nuts”

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  1. I would just add that some (myself included) have difficulty digesting nuts of all types and I personally have discontinued eating them for the most part….

    They “stuff” my system, cause constipation and also inflammation! Definitely not good…

    1. Have you tried crispy nuts? I found the directions in Nourishing Traditions. Soak raw nuts in filtered water with sea salt for about 8 hours. Drain off water and put them in dehydrator around 150 degrees. I used my oven before and put it on lowest temp which was 170 and held door ajar with a wooden spoon to lower the temperature. Nuts are easier to chew, nice and crispy, and they digest better than raw. I believe it is something like soaking grains to make them sprout which makes grains easier to digest also.

  2. Thanks for the answer guys!! I swear I should start paying you for all of the awesome advice you have given me:)

    I eat so many nuts, I’m practically a squirrel;)

  3. Serena,

    Some people choose to soak them (as they would beans) to aid in digestion. Because of the mold issue, I’d keep them in the fridge though and thoroughly dry them first with towels and then spread out on a cookie sheet.

  4. When I first discovered almond butter a few years ago, I thought the gods had personally handed me a gift. I never knew it existed before that. Okay, it would have been a gift if it had come with a lower pricetag!

    And while I can handle most foods in moderation, dark chocolate covered almonds might as well be crack. I can’t have them in the house, or they vanish very very quickly.

    My 4 yo son loves his cashew butter, and my husband sticks with peanut butter mostly, so we’ve got a jar for each of us. YUM!

    1. Thanks for the information that nuts cause constipation. Were they any nuts in particular or do I need to see which ones will give me relief from IBSD? For the most part eating PB has lessened my symptoms; still I can’t enjoy the taste of my favorite vegetables and for the most part all of my favorite vegetables are off limits to anyone with IBSD. So if you would be so kind to let me know which nuts can cause constipation I would be most grateful, Aden

  5. Mark-

    Good stuff, thanks so much! My husband and I are thinking about training for our next marathon, and we have been reading a lot about how certain nuts are extremely beneficial for runners because of the need for additional protein. This post contains a lot of good info on what we needed to know about.

  6. What’s the scoop on cashews? Good? Bad? OK in moderation but almonds and walnuts are better?


    being a legume, they contain, in common with all beans, lectins, which attack the intestinal mucus membrane and, in many people, can cause “leaky gut syndrome” – and thus potentially allow whole proteins into the blood stream and may trigger an auto immune response.


    all the best


  8. I’m with you Crystal, i also eat nuts everyday and love’m! I go to a fresh market and always ask them to grind up “Fresh” Almond Butter before my eyes, can’t beat it!!!

  9. My personal story…I used to put almond butter on everything…especially chicken. Tasted so good. But then there came a time where I stopped….and I noticed something. I felt better….especially when dealing with some small sports related inflammation issues. That and I did more research into the unstable enviroment of most PUFAs (Poly unsat fats) and decided to switch up my fat sources. Now I eat mostly Sat and MUFA (with some Omega 3s from fish oil..and there is still plenty of Omega 6s from meats). I rarely eat nuts….but I still enjoy them time to time….but taking them out of my diet (well I was eating a ton of butter) completely made me feel 100x better.

  10. I started my career working as an engineer in peanut butter product development (P&G, 1959). There wasn’t much said about aflatoxin then, but in the 60’s the lab was testing for it to be sure it wasn’t in their peanuts. However, I got uneasy about other companies who might not test for it especially when I learned it was thought that the aflatoxin mold groth was aided by darkness and moisture on the bags that the peanuts were often harvested and stored in. Then when I heard aflatoxin is an absolute cause of cancer, I gave up peanuts and peanut butter for good.

  11. (2nd comment) I like almond and cashew butter, alone or mixed. A trick I learned in the peanut butter product developement lab that works for these other nut butters is to add a little (olive) oil and a little lecithin when you make nut butter. The lecithin helps yield a smooth butter. The proportions are not real critical – to a cup of nuts, add 1/8 cup oil and (estimated) 1 tsp of lecithin. I also add a little honey, but that’s extra. Then if you have a Vita-Mix, you’re all set. It makes a great nut butter.

  12. Many thanks Mark for the email heads-up to this blog post. Just what I was looking for. Wish you all the best mate!

  13. What I don’t get, is that nuts appear to be quite high in Omega 6 fats. And I thought we were supposed to try to balance out Omega 3 & 6s. Here’s a breakdown of some common nuts, per 100g:

    almonds: 49g total fat, 6mg Omega 3, 12065mg Omega 6, omega6:3 ratio: 2000:1
    cashews: 44g, 63mg, 7782mg, 125:1
    pecans: 72g, 986mg, 20630mg, 20:1
    macadamias: 76g, 206mg, 1296mg, 6:1
    walnuts: 65g, 9079mg, 38092mg, 4:1

    So almonds have virtually NO omega 3 fats, buts HEAPS of omega 6 fats! Only macadamias and walnuts seem to have a reasonable ratio.

    By comparison, canola oil has a 2:1 omega6:3 ratio.

    So all this talk of eating lots of nuts, seems, well, NUTS! Can anyone explain this apparent contradiction?

    All data comes from, which gets it from the USDA.

  14. yes i agree – paleo man would have only had seasonal access, so we should only go nuts for nuts once a year…


  15. While I’m at it, here is the data for peanuts: 49g total fat, 3mg Omega 3, 15555mg Omega 6, omega6:3 ratio: 5185:1.

    So almonds are not really all that different to peanuts, in terms of omega 6.

  16. Mark,

    if you eat the nuts raw – won’t the phytic acid, that works like a nutrience-blocker, hinder things?

    Or do you soak them and gently dry them – making them essentially still raw, but without the phytic acid that exist in the outer layer?

  17. what’s the opinion on macadamia nuts, Mark and everyone? they’re my (and Dr. Atkins’) favorite….

  18. When I started eating primal sure i lost weight but not until I eliminated nuts from my diet.
    For some reason all nuts make me gain weight just like grains do.
    I ditched the nuts and added raw goat’s milk instead (as my treat) and lost another 7 lbs. from 152 down to 145 lbs.

  19. I’m new to primal eating. It seems that nuts are important, but I’m really allergic to them. Any suggestions of how I could get similar nutrients? Thanks!

  20. What’s the consensus on cashews? My nuts are mostly walnuts and almonds (raw and slivered… they’re ridiculously delicious!) but since I’m in college and the only thing they have there are roasted cashews (plus whatever I bring from home) I was wondering where they fall in the Primal hierarchy.

  21. I just started primal a few weeks ago. I’m frustrated because I think I’m eating great but yet again I find another food that I thought was healthy causes cancer or toxin build up. Is it safe to say you can’t avoid all malice from the foods we eat? I’m still eating peanut cause they’re cheap and almonds cause I like them.

  22. What about fresh ground peanut butter? I know the fresh almond butter, but is the fresh ground peanut butter (the kind you grind up yourself) at least an okay occasional treat?

  23. Pretty great post. I simply stumbled upon your weblog and wished to say that I’ve really loved browsing your blog posts. In any case I will be subscribing on your rss feed and I am hoping you write again soon!

  24. Mark – HELP! Our daughter has anaphylactic allergies to peanuts and all tree nuts! Can’t keep them in the house. Are there any other snack foods super high in Omega-3 you can recommend? Greatly appreciate it!

  25. Chia seeds are a plant source that is one of the highest sources of omega 3s. You can sprinkle them on anything. Also, purslane is a weed here in the US, but is a valued potherb and salad herb in other countries and is high in omega 3s. You can mix it with yogurt if you eat dairy for a cold summer salad or mix it in with a tossed greens salad.

  26. I’ve been eating Sun Butter (sunflower seed butter) I’m in love with it I like it way better than Almond Butter

  27. I think that nuts are quite healthy, but you shouldn’t forget about phytic acid which inhibits mineral absorption. Walnuts are the best for heart health (rich in omega-3 fatty acids and oleic acid) so if you’re going to eat nuts in larger amounts, get walnuts!

  28. I having the problem of that many do. I love peanuts, pistacios, walnuts, almonds and cashews. When I eat these “nuts” I break out with cold sore like blisters. Pistacios are the worst and produce the mentioned blisters in half an hours time.

    Since going nut free i have yet to have a break out. I do enjoy soy and sunflower seeds. Does anyone else have the same problem?

  29. I saw your recent article about why we can’t lose weight. You said maybe we ate too many nuts and/or fruit. I love both. I have a few handfuls of almonds and a couple of fruits a day, plus some yummy almond butter on a banana or an apple. I’m a CrossFitter and have lost inches, but no weight. So, how many nuts and fruit are allowed.

    1. From a trained dietitian’s perspective – 2 fruit a day is totally fine to have – especially if you’ve cut out all other processed sources of sugar. As for nuts – if you want weight loss – swap 2 of the handfuls of almonds for a lower fat food choice as nuts are good for you, but high in energy due to their high fat content. If you want to stay strict paleo try making some small paleo muffins based on coconut flour (just google), or chop up some veggies to have with a bit of clean home made salsa or dip.

  30. Phytic acid is actually bound to a small amount of minerals in certain foods, yes- what it doesn’t do is prevent you from absorbing minerals once its inside your gut. It is already bound to a mineral found in the food – so that small amount will pass through your system. It cannot further bind itself to other minerals during the digestion and absorption processes, so I wouldn’t be too concerned about phytic acid.

  31. Mark, what if we prefer roasted and salted macadamias *not too much at one sitting, of course*. Is it also ‘bad’ or is it at least better, compared to other roasted nutty treats?